An FES therapy uses a low-frequency current to stimulate denervated muscles, making muscle contraction in order to replace or correct functions that organs and limbs have lost. Currently, research and application on FES have been involved in various fields of clinical treatment. In general, an FES device is a portable stimulator with two to four channels.
A diaphragm pacemaker for controlling and regulating a respiratory movement is an FES system. This system is used to cure respiratory muscle paralysis caused by cerebrovascular disease, brain trauma or high-level spinal cord injury. A pair of electrodes is implanted in bilateral phrenic nerves or surface electrodes are placed on the motor point of the phrenic nerve of the bilateral neck. Then the electrodes are connected to a signal receiver fixed on a chest wall. A controller sends a wireless pulse signal and the receiver converts the wireless pulse signal into a low-frequency current, which stimulates the phrenic nerve through the electrodes to cause the diaphragm contraction.
Further, FES has implemented benefits in treatment of voiding dysfunction. Taking urinary incontinence as an example, it causes myasthenia of the urethral sphincter and pelvic floor muscle due to lower motor neuron injury, causing endless urination dripping or urination just because abdominal pressure slightly increases. On clinical uses, FES stimulates the urethral sphincter and pelvic floor muscle to enhance their muscle strength, which can improve the degree of urinary incontinence significantly. Another example is when the sacral cord micturition center injures, the detrusor muscle is paralyzed and urinary retention occurs. Implanted electrodes are usually used in a clinic to stimulate the detrusor muscle, making this muscle contraction in order to overcome the pressure of the urethral sphincter and empty the bladder.
In addition, the FES therapy can used for upper motor neuron injury to complete some functional activities, such as walking, grasping, and coordinated movement, which can accelerate recovery of voluntary control. The upper motor neuron injury may include cerebrovascular disease, brain trauma, spinal cord injury, cerebral palsy, etc. Limb movement is critical to the rehabilitation of these users, especially users with spinal cord injury. A study found that the electrical signal generated by the limb movement, can cause irritation on the spinal cord stump, which achieves the restoration of part of the spinal cord continuity. Some scientists have proposed a FES-assisted treadmill training method, which can restore muscle strength and promote local tissue repair of spinal cord injury.